<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
  <canvas id="canvas" width="400" height="400" style="background: gray">
      此浏览器不支持canvas
  </canvas>
</body>
</html>

<script>
    const ctx = document.getElementById('canvas')

    const c = ctx.getContext('2d')

    c.fillStyle = 'red'
    c.fillRect(10, 10, 100, 100)

</script>
